A number of power tools have been produced to facilitate forming a work piece into a desired shape. One such power tool is a saw device. A wide range of saw device are available for a variety of uses. For example, some saw device such a cabinet table saws are very heavy and relatively immobile. Other table saws, sometimes referred to as jobsite table saws, are relatively light. Jobsite table saws are thus portable so that a worker can position the table saw at a job site. Some accuracy is typically sacrificed in making a table saw sufficiently light to be mobile. The convenience of locating a table saw at a job site, however, makes job site table saws very desirable in applications such as general construction projects.
All table saws, including cabinet table saws and job site table saws, present a safety concern because the saw blade of the table saw is typically very sharp and moving at a high rate of speed. Accordingly, severe injury such as severed digits and deep lacerations can occur almost instantaneously. A number of different safety systems have been developed for table saws in response to the dangers inherent in an exposed blade moving at high speed. One such safety system is a blade guard. Blade guards movably enclose the saw blade, thereby providing a physical barrier that must be moved before the rotating blade is exposed. While blade guards are effective to prevent some injuries, the blade guards can be removed by a user either for convenience of using the table saw or because the blade guard is not compatible for use with a particular shaping device. By way of example, a blade guard is typically not compatible with a dado blade and must typically be removed when performing non-through cuts.
Table saw safety systems have also been developed which are intended to stop the blade when a user's hand approaches or touches the blade. Various stopping devices have been developed including braking devices which are physically inserted into the teeth of the blade. More recently, systems have been developed which physically move the blade or other shaping instrument below the support surface of the device. One such device incorporates a swing arm assembly which supports a blade above a work piece support surface and swings the blade beneath the work piece support surface when an unsafe condition is sensed. Regardless of the mechanism which is used to physically render a power tool safe, an associated control system must be functional. This is particularly important in systems which incorporate single use devices such as a pyrotechnic charge to move a blade away from a user.
In view of the foregoing, it would be advantageous to provide a power tool with a mitigation system that evaluates the operational status of the mitigation system. A mitigation system that evaluates the same circuitry used to activate a mitigation mechanism would also be advantageous.